Process for the manufacture of dispersible alumino-silicates

ABSTRACT

The present invention relates to a process for the manufacture of high-purity alumino-silicates which are dispersible in aqueous and/or aqueous-acidic media by hydrolysis of aluminium compounds and silicic acid compounds and hydrothermal treatment.

The present invention relates to a process for the manufacture ofhigh-purity alumino-silicates which are dispersible in aqueous oraqueous-acidic media by hydrolysis of aluminium compounds and silicicacid compounds and hydrothermal treatment.

There exists a large number and wide variety of naturalalumino-silicates, including many compounds having defined crystallinestructures, such as muscovite, nepheline, and chabasite. When exchangingpart of the silicon atoms in the reticulation of silicates for aluminiumatoms, while maintaining the reticulation, zeolites are obtained.

Besides natural alumino-silicates, there are many synthetic products ofthis kind. Such products may be those defined by crystal chemistry ormay be physical mixtures of aluminium hydroxide and silicic acids withdifferent quantities of water. Besides physical mixtures,alumino-silicate defined by crystal chemistry may be present as well.

A customary process for preparing such alumino-silicates is theconversion of clays, such as kaolin, using silicic acid and sodiumhydroxide. Another synthesis route is the cogelation of aluminiumhydroxide sols with silicic acid sols followed by precipitation [cf. GB2166971-C]. Precipitation of an aluminium salt in a silicic acid sol isknown as well [cf. CA 848966-A].

The aforesaid processes have the disadvantage that the desired sols oremulsions only exist at the instant they are prepared, while the powderobtained by subsequent drying can only incompletely be dispersed orrequires solvent mixtures to achieve dispersion. Another disadvantage isthat the sols or emulsions prepared in this way contain large quantitiesof alkali metals or alkaline earth metals used for stabilising thesilicic acid. Subsequent purification, e.g. by ion exchange, isincomplete and results in typical concentrations of alkali metals oralkaline earth metals of 0.1% (equal to 1,000 ppm) after purification[cf. U.S. Pat. No. 3,933,6211].

Heterogeneous catalysis requires high-purity catalyst supportscontaining less than 100 ppm of alkali metals and/or alkaline earthmetals, particularly less than 50 ppm of sodium oxide. The preparationof such high-purity alumino-silicates using ion exchanged ortho-silicicacid is described in German patent DE 38 39 580-C1. The resultantalumino-silicates have the desired high purities, but they cannot bedispersed.

Alumino-silicates are physically/chemically not comparable withaluminium hydroxides. For instance, their surfaces have higher aciditiesdue to the stronger Lewis acid character of silicic acid. This propertyis utilized for a large number of catalytic processes, such asdesulfurizing, denitrification, oxidation, hydrocracking, and mildhydrocracking.

Modern catalysts often consist of many different support materials [forinstance, cf. GB 2166971-C]. It is essential that the catalyst supportmaterials be homogeneously mixed to ensure uniform compositions.Therefore, dispersible alumino-silicates offer several advantages, e.g.when used for coating substrates. This method can be used in the fieldof catalysis and materials coating. The explanations given hereinaboveshow that there is a need for dispersible high-purity alumino-silicates.

It was the object of this invention to develop a synthesis for preparingdispersible alumino-silicates which offers the following advantages:

Even after drying and conversion into powder, the alumino-silicatesprepared according to the present invention shall be dispersible inaqueous solutions without addition of or treatment with organicsolvents.

The alumino-silicates prepared according to the present invention shallhave high purities.

The starting materials used for preparing the aforesaid compounds shallbe readily available.

The price of the starting materials shall allow an economic process.

The manufacturing process shall be feasible both as a continuous anddiscontinuous process.

It was surprisingly found that the process described hereinbelowprovides alumino-silicates which solve the problems the presentinvention was based on.

The instant invention relates to a process for the continuous ordiscontinuous manufacture of high-purity alumino-silicates which can bedispersed in aqueous and/or aqueous-acidic media. The desired propertiesare obtained by the following process:

Process for the manufacture of alumino-silicates which are dispersiblein aqueous and/or aqueous-acidic media wherein

(A) one or more hydrolyzable aluminium compound(s) is (are) hydrolyzedjointly or discontinuously in space or time, preferably jointly, and

(B) said compound(s) is (are) contacted with one or more silicic acidcompound(s) prior to, during, or after hydrolysis, preferably prior toor during hydrolysis, and

(C) the combined compounds/reaction products are jointly subjected tohydrothermal ageing in an aqueous environment and in the presence of amonovalent organic C₁ to C₆ acid or a monovalent inorganic acid attemperatures of 40 to 220° C. for a period of more than 0.5 h during orafter hydrolysis.

The hydrolysis may be carried out at 20 to 98° C., preferably 50 to 98°C., most preferably 85 to 98° C. Hydrolyzable aluminium compounds withinthe meaning of the instant invention are all the aluminium compoundsforming Al—OH and/or Al—O—Al structures when reacted with water, e.g.aluminium alcoholates, aluminium hydroxyalcoholates, aluminiumoxyalcoholates, aluminium acetyl acetonates, aluminium alkyl chlorides,or aluminium carboxylates. Preferably, the hydrolyzable aluminiumcompounds are compounds of the type Al(O-R-A-R′)_(3−n)(O-R″)_(n),wherein independent of each other and, optionally, different for eachresidue

R″ is a branched or an unbranched, a cyclic or an acyclic, or anaromatic hydrocarbon residue having 1 to 30, particularly 2 to 12 carbonatoms,

R′ is a branched or an unbranched, a cyclic or an acyclic, or anaromatic hydrocarbon residue having 1 to 10 carbon atoms, particularlyan alkyl residue having 4 to 8 carbon atoms,

R is a bivalent and branched or unbranched, cyclic or acyclic, oraromatic C₁ to C₁₀ hydrocarbon residue, particularly an alkyl residuehaving 1 to 5 carbon atoms, most preferably 1 to 3 carbon atoms, thelatter one most preferably being unbranched and acyclic,

A represents a heteroatom of main group 6 (oxygen group) or main group 5(nitrogen group) of the periodic system, preferably oxygen or nitrogen,wherein, if A represents an element of main group 5, A bears hydrogen ora C₁ to C₁₀ alkyl residue or a C₆ to C₁₀ aryl-/alkyl aryl residue asadditional substituent(s) for the saturation of its valences, and

n is an index for the numbers 0, 1, 2, or 3.

Preferably, n is equal to 0 or equal to 3. In case n is equal to 0 and Ais equal to oxygen, aluminium trisbutylene glycolates are preferred.

In case n is equal to 3, the aluminium alkoxy compounds are aluminiumtrisalcoholates which, with increasing preference, have C₂ to C₁₂, C₄ toC₈, or C₆ to C₈ hydrocarbon residues, the residues being saturated orunsaturated, cyclic or acyclic, branched or unbranched, or aromatic,preferably saturated. Saturated, linear C₆ to C₈ hydrocarbon residuesare particularly preferred. For example, hydrolyzable aluminiumalcoholates may be prepared according to the process disclosed in EP 0111 115-A1.

Prior to use, the hydrolyzable metal compounds may be purified bydistillation, filtration, or centrifugation. In the case of silicicacid, ion exchange of metal ions, particularly sodium, preferably onexchange resins containing ammonium ions, is an efficient purificationmethod.

For the hydrothermal treatment, it is essential that an acid be presentduring or after hydrolysis. This acid is a monovalent organic C₁ to C₆acid or a monovalent inorganic acid (or a monovalent mineral acid), suchas HCl or HNO₃. The acid may also be added after hydrolysis, as long asit is present during the hydrothermal treatment. According to thepresent invention, the acid or an acid-forming agent is added prior tothe first drying of the alumino-silicate.

Within the meaning of the present invention, monovalent organic C₁ to C₆acids are organic compounds which have at least 1 to 6 carbon atoms andshow an acid reaction in the presence of water, i.e. react as protondonators, and which can set free only one proton, referring to the acidmolecule. Included in this definition are for instance acid chlorides,sulfonic acids, and other organic compounds forming —COOH or —COO⁻groups in water.

The acid is added in quantities of 0.1 to 2.0 gram, preferably 0.2 to0.8 gram, referring to 1 gram of solid material. Hydrothermal ageingpreferably takes 1 to 22 hours. A period of 2 to 18 hours andtemperatures of 80 to 130° C. have proved to be particularly efficient.

It is another outstanding feature of the process according to thepresent invention that, apart from the educts and products, the reactioncan be performed without any organic solvent and in an essentiallyalcoholic/aqueous environment, an aqueous environment being preferred.

The educts Al₂O₃ and SiO₂ may be used in quantities of from 99.5 wt. %:0.5 wt. % to 70 wt. %: 30 wt. %, preferably from 98 wt. %: 2 wt. % to 70wt. % : 30 wt. %, each referring to the ratio of Al₂O₃: SiO₂.Furthermore, the reaction product of this invention may be calcined attemperatures of 550° C. to 1,500° C. for a period of 0.5 to 24 hours.

The dispersible alumino-silicates are useful as catalysts, catalystsupports for catalytic processes, for the manufacture of catalysts, asstarting materials for ceramics, as coating materials, and as bindercomponents and rheological modifiers in aqueous systems.

The silicic acid compounds used according to this invention are forexample condensation products of orthosilicic acid, particularly the lowcondensation products thereof, and most preferably orthosilicic aciditself. The silicic acid compounds used according to the presentinvention can also be manufactured in situ by hydrolysis of silicontetrachloride. Water is preferably used for the hydrolysis.

By the term ‘dispersible alumino-silicates’ as used in the presentinvention are meant dry and, most expediently, powdery alumino-silicateswhich can be dispersed in aqueous media in quantities of at leastgreater than 90 wt. %, preferably greater than 95 wt. %, i.e.greaterthan 90 wt. %, preferably greater than 95 wt. % of said products willremain dispersed after dispersion. In the experimental part describedhereinbelow a method for quantifying the dispersibility is described.The resultant aqueous products can be dried using known methods, such asspray drying or by means of a rotary drier. The process formanufacturing alumino-silicates according to this invention can becarried out continuously or discontinuously.

The alumino-silicates of this invention can be dispersed usingwater-diluted acids, such as inorganic, monovalent acids, e.g.hydrochloric acid or nitric acid, or C₁ to C₆ organic acids, monovalentacids being preferred. The acids used for dispersion can be employed inconcentrations of 0.1 to 40 wt. %, referring to the straight acid.Preferably, lower concentrations are used, i.e. from 0.1 to 5 wt. %. Insome cases it is also possible to use only water for dispersion.

The compounds manufactured according to this invention can be calcinedin a furnace at temperatures of preferably 550° C. to 1,500° C. for aperiod of preferably 3 to 24 hours. The metal oxide manufactured in thisway has the requisite high purity.

Table 1, following, shows several alumino-silicates manufacturedaccording to the present invention and their dispersibilities D.

TABLE 1 Al₂O₃:SiO₂ HNO₃ Ageing Dispersibility D Compound [wt. %:wt. %][wt. %] [h/° C.] [%] 1 95.0:5.0 0.5 16 h/95° C.  98 2 90.5:9.5 0.8 16h/95° C.  95 3 94.9:5.1 0.6 5 h/95° C. 97 4 90.7:9.3 1.0 5 h/95° C. 96 570.5:29.5 — 5 h/95° C. 99 A 95.1:4.9 30 — nondispersible B 50.4:49.6 30— nondispersible C 68.8:31.2 30 5 h/95° C. nondispersible Legend:Compounds A and B are conventionally produced alumino-silicates. C is analumino-silicate prepared according to this invention, includinghydrothermal treatment, but without addition of an acid A through C arereference substances; 10 weight percent of each solid alumino-silicatewere dispersed * acid for dispersion

Table 2, following, shows the physical data of the alumino-silicatesaccording to this invention in comparison with two standardalumino-silicates (A and B). The reference alumino-silicates A and Bwere prepared by mixing an alumina sol with silicic acid.

TABLE 2 Al₂O₃:SiO₂ Surface Pore Volume Compound [wt. %] [m²/g] [ml/g] 195.0:5.0 368 0.50 2 90.5:9.5 409 0.50 3 94.9:5.1 350 0.49 4 90.7:9.3 3640.48 5 70.5:29.5 246 0.11 A 95.1:4.9 314 0.54 B 50.4:49.6 452 0.60

The dispersible alumino-silicates manufactured according to thisinvention have high purities. In particular. the content of alkalimetals and alkaline earth metals which have particularly adverse effectswhen using the aforesaid products for catalysis is very low. The resultsof the trace elements analysis by ICP spectroscopy are listed in Table3. The purities listed in Table 3 can be further increased by usingbidistilled water and containers made of inert materials.

TABLE 3 Na₂O Li₂O MgO CaO TiO₂ Fe₂O₃ Compound [ppm] [ppm] [ppm] [ppm][ppm] [ppm] 1 <10 <5 <10 <10 <50 50 2 <10 <5 <10 <10 <50 34 3 15 <5 <10<10 <50 28 Legend: The concentration of other elements, such as Pb, Zn,Ni, Cr, Cu, Mn, Mo, and Ga, is less than 50 ppm in total.

EXAMPLES (GENERAL)

The compounds manufactured according to this invention were analysed fortrace impurities by inductively coupled plasma (ICP) spectroscopy. Thesurfaces were determined by the BET method, while the pore volumes wereadditionally determined by mercury porosimetry (Autopore II 9220porosimeter, Mikromeritics) and nitrogen porosimetry (Flow Prep 060,Gemini 2360, 2375, Mikromeritics). The compounds of this Invention werecalcined in a muffle furnace at temperatures of between 550° C. and1,500° C. Delonised water was used for the hydrolysis.

The dispersibility D was determined by the following method. A certainamount of the dry, solid material was placed into a beaker and mixedwith dilute acid, e.g. nitric acid, while stirring. Stirring wascontinued for 10 minutes (stirrer speed 800-850 rpm). The suspensionthus obtained was quantitatively transferred to the glass tube of acentrifuge. Subsequent to centrifugation for 20 minutes at 2,400 rpm⁻¹,the supernatant was decanted, and the residue in the glass tube wasdried for at least 0.5 hour at 573 K (300° C.). The glass tube then wasweighed including the residue, and thereafter without residue. Thedifference obtained is the weight of nondispersed solid.$\text{Nondispersed quantity, \%} = \frac{\text{gram of residue} \times 100}{\text{initial weight of alumina, in grams}}$Dispersed quantity  D,  % = 100 − percentage of nondispersed quantity

Example 1 (Compound 1)

Into a 2,000-ml three-neck flask, there were placed 487 grams of waterand 87.7 grams of aqueous silicic acid (3.6 wt. %). The contents washeated to 75° C. A total of 500 grams of aluminium trishexanolate (6.35wt. % Al content) were added to this mixture in three portions at timeintervals of 15 minutes each. The mixture was stirred for 30 minutes.Then, 6.3 grams of 65% nitric acid were added. The alcohol was decantedand the residue was diluted to a desired solids content of about 5%. Thesol was heated to 95° C. and maintained at this temperature for 16hours. The remaining aqueous phase was liberated from alcohol residue bysteam distillation, followed by spray drying.

Example 2 (Compound 2)

Into a 2,000-ml three-neck flask, there were placed 390 grams of waterand 185 grams of aqueous silicic acid (3.6 wt. %). The contents washeated to 75° C. A total of 500 grams of aluminium trishexanolate (6.35wt. % Al content) were added to this mixture in three portions at timeintervals of 15 minutes each. The mixture was stirred for 30 minutes.Then, 6.7 grams of 65% nitric acid were added. The alcohol was decantedand the residue was diluted to a solids content of about 5%. The sol washeated to 95° C. and maintained at this temperature for 16 hours. Theremaining aqueous phase was liberated from alcohol residue by steamdistillation, followed by spray drying.

Example 3 (Compound 3)

Into a 2,000-ml three-neck flask, there were placed 490 grams of waterand 78.3 grams of aqueous silicic acid (4.0 wt. %). The contents washeated to 75° C. A total of 500 grams of aluminium trishexanolate (6.3wt. % Al content) were added to this mixture in three portions at timeintervals of 15 minutes each. The mixture was stirred for 30 minutes.Then, 6.3 grams of 65% nitric acid were added. The alcohol was decantedand the residue was diluted to a solids content of about 5%. The sol washeated to 95° C. and maintained at this temperature for 5 hours. Theremaining aqueous phase was liberated from alcohol residue by steamdistillation, followed by spray drying.

Example 4 (Compound 4)

Into a 2,000-ml three-neck flask, there were placed 383 grams of waterand 185 grams of aqueous silicic acid (3.6 wt. %). The contents washeated to 75° C. A total of 500 grams of aluminium trishexanolate (6.35wt. % Al content) were added to this mixture in three portions at timeintervals of 15 minutes each. The mixture was stirred for 30 minutes.Then, 6.7 grams of 65% nitric acid were added. The alcohol was decantedand the residue was diluted to yield a solids content of about 5%. Thesol was heated to 95° C. and maintained at this temperature for 5 hours.The remaining aqueous phase was liberated from alcohol residue by steamdistillation, followed by spray drying.

Example 5 (Compound 5)

Into a 2,000-ml three-neck flask, there were placed 654 grams of aqueoussilicic acid (3.9 wt. %) and 67 grams of nitric acid (65 wt. %). Thecontents was heated to 75° C. A total of 500 grams of aluminiumtrishexanolate (6.3 wt. % Al content) were added to this mixture inthree portions at time intervals of 15 minutes each. The mixture wasstirred for 30 minutes. The sol was heated to 95° C. and maintained atthis temperature for 5 hours, followed by dilution to a solids contentof about 5%. The supernatant alcohol was decanted and the remainingaqueous phase was liberated from alcohol residue by steam distillation,followed by spray drying.

Example 6 (Compound 6)

Into a 2,000-ml three-neck flask, there were placed 638 grams of aqueoussilicic acid which were heated to 75° C. A total of 500 grams ofaluminium trishexanolate (6.35 wt. % Al content) were added in threeportions at time intervals of 15 minutes each. The mixture was stirredfor 30 minutes. The alcohol was decanted and the residue was diluted toa solids content of about 5%. The sol was heated to 95° C. andmaintained at this temperature for 5 hours. The remaining aqueous phasewas liberated from alcohol residue by steam distillation, followed byspray drying.

What is claimed is:
 1. A process for manufacturing alumino-silicatesthat are dispersible in aqueous and/or aqueous-acidic mediacharacterized in that: (a) at least one hydrolyzable aluminium compoundis hydrolyzed; (b) prior to, during, or after hydrolysis, said aluminiumcompound is contacted with at least one silicic acid compound; (c) priorto, during, or after the hydrolysis, a monovalent C₁ to C₆ acid or amonovalent inorganic acid is added to produce an acidified mixturecontaining said monovalent acid, said at least one silicic acidcompound, and said at least one aluminium compound; and (d) theacidified mixture is hydrothermally aged in an aqueous medium in thepresence of said monovalent acid at a temperature of 40 to 220° C. for aperiod of more than 0.5 hours to form a reaction product, using analuminium compound-silicon compound ratio ranging from 99.5 wt. %:0.5wt.% to 70 wt. %:30 wt. % based on the ratio of Al₂O₃: SiO₂.
 2. The processof claim 1 wherein there are a plurality of hydrolyzable aluminiumcompounds and silicic acid compounds.
 3. The process according to claim1, further comprising a step of calcinating the reaction product.
 4. Aprocess according to claim 1, characterized in that the hydrolyzablealuminium compound is a compound having formulaAl(O—R—A—R′)_(3−n)(O—R″)_(n), wherein: “R″” is a hydrocarbon residuehaving 1 to 30 carbon atoms; “R′” is a hydrocarbon residue having 1 to10 carbon atoms; “R” is a bivalent hydrocarbon residue having 1 to 10carbon atoms; “A” represents a heteroatom selected from the groupconsisting of the main group 6 (oxygen group) and the main group 5(nitrogen group) of the periodic system; and “n” is an index for thenumbers 0, 1, 2, or
 3. 5. A process according to claim 4, characterizedin that n is equal to
 0. 6. A process according to claim 4,characterized in that n is equal to
 3. 7. A process according to any oneof claims 4, 5, or 6, characterized in that the hydrolyzable aluminiumcompound is an aluminium alcoholate having C₂ to C₁₂ hydrocarbonresidues.
 8. The process of claim 7 wherein the aluminium alcoholate hasC₄ to C₈ hydrocarbon residues.
 9. The process of claim 7 wherein thealuminium alcoholate has C₆ to C₈ hydrocarbon residues.
 10. A processaccording to any one of claims 4-6, characterized in that orthosilicicacid and/or condensation products thereof are used as the silicic acidcompound.
 11. A process according to any one of claims 4-6,characterized in that the hydrolyzable aluminium compound is firstpurified by distillation, filtration, or centrifugation, and/or thesilicic acid compound is liberated from metal ions by ion exchange. 12.The process of claim 11 wherein said ion exchange is carried out on anion exchange resin containing ammonium ions.
 13. A process according toany one of claims 4-6, characterized in that the hydrolysis is performedat 20 to 98° C.
 14. The process of claim 13 wherein said hydrolysis isperformed at 85 to 98° C.
 15. A process according to any one of claims4-6, characterized in that the monovalent acid is added after thehydrolysis and prior to or during the hydrothermal treatment.
 16. Aprocess according to any one of claims 4-6, characterized in that thehydrothermal aging is conducted for a period of 0.5 hour to 24 hours.17. The process of claim 16 wherein said hydrothermal aging is conductedfor a period of 2 to 18 hours.
 18. A process according to any one ofclaims 4-6, characterized in that the hydrothermal aging is conducted at80 to 130° C.
 19. A process according to any of claims 4-6,characterized in that the reaction product is calcined at temperaturesof between 550° C. and 1500° C. for a period of 0.5 hour to 24 hours.20. The process of claim 4 wherein A is an element of main group 5 and Abears a hydrogen or a C₁ to C₁₀ alkyl residue, or a C₆ to C₁₀aryl-/alkyl-aryl residue as additional substituents for saturation ofits valences.